How do I permanently resize a model with children?

Questions & Answers
1

I am in the process of building some tools for level creation and asset management. We have a need to be able to permanently resize models to 1.0 unity units max, x, y, or z. Working from a solution provided by @robertbu, I have devised a script which works great for objects which have no children. However, I am having an issue with resizing objects which do have children. I have a function right now which will cycle through the bounds of the children to determine the total bounds of the object, and then resize their meshes and translate their positions relative to the parent, using a calculated scale.

The problem is that the meshes stay permanently resized as they should, but the new positions only apply to the instance, resulting in models whose children resize smaller and smaller every time they are placed because the new positions never permanently applied. How can I permanently change the child mesh positions relative to the parent?

Here is the function I am currently working with:

	void ResizeMeshToUnit(GameObject g) {
		int count = g.transform.GetChildCount();
		float minX, minY, minZ, maxX, maxY, maxZ, finalX, finalY, finalZ, size;
		
		//initialize variables.
		finalX = finalY = finalZ = size = 0f;
		minX = maxX = g.transform.position.x;
		minY = maxY = g.transform.position.y;
		minZ = maxZ = g.transform.position.z;
		
		if (count < 1)
		{
			return;
		}
		
		//cycle through children bounds to get minimums and maximums for model
		for (int i = 0; i < count; i++) {
			Transform t = g.transform.GetChild(i);
			var renderer = t.GetComponent<Renderer>();
			
		    if (renderer != null)
			{
		    	Bounds bounds = renderer.bounds;
	     
			    if (bounds.min.x < minX)
				{
			    	minX = bounds.min.x;
				}
				if (bounds.min.y < minY)
				{
			    	minY = bounds.min.y;
				}
			    if (bounds.min.z < minZ)
				{
			    	minZ = bounds.min.z;
				}
				
				if (bounds.max.x > maxX)
				{
			    	maxX = bounds.max.x;
				}
				if (bounds.max.y > maxY)
				{
			    	maxY = bounds.max.y;
				}
			    if (bounds.max.z > maxZ)
				{
			    	maxZ = bounds.max.z;
				}
			}
		}
		
		//establish overall bounds
		finalX = maxX - minX;
		finalY = maxY - minY;
		finalZ = maxZ - minZ;
	    
		//determine largest dimension
		size = finalX;
	    if (size < finalY)
		{
	    	size = finalY;
		}
	    if (size < finalZ)
		{
	    	size = finalZ;
		}
		
		//return if already correct scale
	    if (Mathf.Abs(1.0f - size) < 0.01f)
		{
	    	Debug.Log ("Already unit size");
	    	return;
	    }
		
		//calculate scale
	    float scale = 1.0f / size;
		
		//use scale to resize child meshes and alter positions
		for (int i = 0; i < count; i++)
		{
			Transform t = g.transform.GetChild(i);
			
		    MeshFilter mf = t.GetComponent<MeshFilter>();
		    if (mf != null)
			{
		    	Mesh mesh = mf.sharedMesh;
				t.localPosition *= scale;
				
				Vector3[] verts = mesh.vertices;
		     
			    for (int j = 0; j < verts.Length; j++)
				{
			    	verts[j] = verts[j] * scale;
			    }
			     
			    mesh.vertices = verts;
			    mesh.RecalculateBounds();
			    mesh.RecalculateNormals();
			}
		}
	}

How can I get the positions to permanently stick in the model?

EDIT:
The original question, which @robertbu provided a working approach for can be found here:
http://answers.unity3d.com/questions/495977/how-do-i-scale-an-object-or-prefab-to-a-size-in-un.html

EDIT 2: Solution has been worked out and is contained in an an answer below.

2

LATER …

dude, I think you’re looking for the famous encapsulate function

you use it constantly with bounds … it makes things so easy

Does that help!?

EARLIER …

Shouldn’t you just be changing the scale of the actual model on the importer ?

3

I thought I would provide a solution to this issue here, so that those who took the time to help me can see what I came up with, and so that others can possibly learn from it. I ended up utilizing the direction provided by @Fattie and @whydoidoit, combining the elegant use of the encapsulate function, and looking hard at the capabilities of the the AssetPostProcessor class to create a script which will scale an object to a maximum of 1 Unity unit on any axis upon importing.

On Preprocessing the import, the script first sets the FBX globalscale to 1. Then, in Postprocessing, the script calculates the ratio necessary to resize the model into Unity units, and the model is then scaled down in size, before being written to the disk. The benefit here is that the change is “semi-permanent”, in that any instances of this model will contain the same scale. The script works great, and will scale models to exact size, without sacrificing the quality of animations which are added afterwards. Thanks again @Fattie and @whydoidoit:

using UnityEngine;
using System.Collections;
using UnityEditor;
     
class MeshPostprocessor : AssetPostprocessor {
	
	float desiredSizeInUnits = 1.0f;
	
	void OnPreprocessModel ()
	{
		ModelImporter importer = (ModelImporter)assetImporter;
		importer.globalScale = 1f;
	}
	
	void OnPostprocessModel (GameObject g)
	{
		Bounds combinedBounds = new Bounds(g.transform.position, new Vector3(0, 0, 0));
		Renderer[] renderers = g.GetComponentsInChildren<Renderer>();
		
		foreach (Renderer r in renderers)
		{
			combinedBounds.Encapsulate(r.bounds);
		}
		
		float size = combinedBounds.size.x;
		if (size < combinedBounds.size.y)
		{
			size = combinedBounds.size.y;
		}
		if (size < combinedBounds.size.z)
		{
			size = combinedBounds.size.z;
		}
	     
		if (Mathf.Abs(desiredSizeInUnits - size) < 0.01f)
		{
			return;
		}
	     
		float scale = desiredSizeInUnits / size;
		g.transform.localScale *= scale;
	}
}